De Klassieker (English: "The Classic") is the main football rivalry of the Netherlands. It is between Ajax, of Amsterdam and Feyenoord, of Rotterdam and is highly contested. The record attendance was on 9 January 1966, when 65,562 watched in Rotterdam. [1]

There have been many clashes between the supporters of both clubs, of which Beverwijk (see Battle of Beverwijk) in 1997 was infamous. One Ajax fan, Carlo Picornie, was beaten to death by rival supporters, triggering more strict policies from the Dutch football association KNVB to tackle hooliganism. As a result of the incident, the two Klassiekers in 1997/98 were played without away fans. Nevertheless, in April 2005, riots took place around Feyenoord's ground involving hooligans from both sides and the riot police. Travelling Ajax fans had demolished the train transporting them to Rotterdam, and were forced to wait outside the stadium until the match was over. Meanwhile, Feyenoord supporters who had just seen their team lose, were determined to clash with rivals from Amsterdam, who had not seen the match.

Hooligans filmed by police were shown on national TV. Virtually every hooligan on TV handed himself in.

In February 2009, the mayors of Amsterdam and Rotterdam made an agreement with the KNVB to ban visiting fans from the away games for the next five seasons in an effort to curb the violence.